
// This file is part of the mstp-lib library, available at http://code.google.com/p/mstp-lib/ 
// Copyright (c) 2011-2014 Adrian Gostin, distributed under the GNU General Public License v3.

#include "hmac_md5.h"
#include "assert.h"
#include <string.h>

static void Transform (unsigned int *buf, unsigned int* in);

static unsigned char PADDING[64] = {
	0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

/* F, G and H are basic MD5 functions: selection, majority, parity */
#define F(x, y, z) (((x) & (y)) | ((~x) & (z)))
#define G(x, y, z) (((x) & (z)) | ((y) & (~z)))
#define H(x, y, z) ((x) ^ (y) ^ (z))
#define I(x, y, z) ((y) ^ ((x) | (~z))) 

/* ROTATE_LEFT rotates x left n bits */
#define ROTATE_LEFT(x, n) (((x) << (n)) | ((x) >> (32-(n))))

/* FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4 */
/* Rotation is separate from addition to prevent recomputation */
#define FF(a, b, c, d, x, s, ac) \
{(a) += F ((b), (c), (d)) + (x) + (unsigned int)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}
#define GG(a, b, c, d, x, s, ac) \
{(a) += G ((b), (c), (d)) + (x) + (unsigned int)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}
#define HH(a, b, c, d, x, s, ac) \
{(a) += H ((b), (c), (d)) + (x) + (unsigned int)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}
#define II(a, b, c, d, x, s, ac) \
{(a) += I ((b), (c), (d)) + (x) + (unsigned int)(ac); \
	(a) = ROTATE_LEFT ((a), (s)); \
	(a) += (b); \
	}

static void MD5Init (MD5_CTX* mdContext)
{
	mdContext->i[0] = mdContext->i[1] = 0;

	// Constant from table 13-1, page 333 in 802.1Q-2011
	mdContext->buf[0] = 0x67452301u;
	mdContext->buf[1] = 0xefcdab89u;
	mdContext->buf[2] = 0x98badcfeu;
	mdContext->buf[3] = 0x10325476u;
}

static void MD5Update (MD5_CTX* mdContext, const unsigned char* inBuf, unsigned int inLen)
{
	unsigned int in[16];
	int mdi;
	unsigned int i, ii;

	/* compute number of bytes mod 64 */
	mdi = (int)((mdContext->i[0] >> 3) & 0x3F);

	/* update number of bits */
	if ((mdContext->i[0] + ((unsigned int)inLen << 3)) < mdContext->i[0])
		mdContext->i[1]++;
	mdContext->i[0] += ((unsigned int)inLen << 3);
	mdContext->i[1] += ((unsigned int)inLen >> 29);

	while (inLen--) {
		/* add new character to buffer, increment mdi */
		mdContext->in[mdi++] = *inBuf++;

		/* transform if necessary */
		if (mdi == 0x40) {
			for (i = 0, ii = 0; i < 16; i++, ii += 4)
				in[i] = (((unsigned int)mdContext->in[ii+3]) << 24) |
				(((unsigned int)mdContext->in[ii+2]) << 16) |
				(((unsigned int)mdContext->in[ii+1]) << 8) |
				((unsigned int)mdContext->in[ii]);
			Transform (mdContext->buf, in);
			mdi = 0;
		}
	}
}

static void MD5Final (MD5_CTX* mdContext, unsigned char* digest)
{
	unsigned int in[16];
	int mdi;
	unsigned int i, ii;
	unsigned int padLen;

	/* save number of bits */
	in[14] = mdContext->i[0];
	in[15] = mdContext->i[1];

	/* compute number of bytes mod 64 */
	mdi = (int)((mdContext->i[0] >> 3) & 0x3F);

	/* pad out to 56 mod 64 */
	padLen = (mdi < 56) ? (56 - mdi) : (120 - mdi);
	MD5Update (mdContext, PADDING, padLen);

	/* append length in bits and transform */
	for (i = 0, ii = 0; i < 14; i++, ii += 4)
		in[i] = (((unsigned int)mdContext->in[ii+3]) << 24) |
		(((unsigned int)mdContext->in[ii+2]) << 16) |
		(((unsigned int)mdContext->in[ii+1]) << 8) |
		((unsigned int)mdContext->in[ii]);
	Transform (mdContext->buf, in);

	/* store buffer in digest */
	for (i = 0, ii = 0; i < 4; i++, ii += 4) {
		digest[ii] = (unsigned char)(mdContext->buf[i] & 0xFF);
		digest[ii+1] =
			(unsigned char)((mdContext->buf[i] >> 8) & 0xFF);
		digest[ii+2] =
			(unsigned char)((mdContext->buf[i] >> 16) & 0xFF);
		digest[ii+3] =
			(unsigned char)((mdContext->buf[i] >> 24) & 0xFF);
	}
}

/* Basic MD5 step. Transform buf based on in.
*/
static void Transform (unsigned int *buf, unsigned int* in)
{
	unsigned int a = buf[0], b = buf[1], c = buf[2], d = buf[3];

	/* Round 1 */
#define S11 7
#define S12 12
#define S13 17
#define S14 22
	FF ( a, b, c, d, in[ 0], S11, 3614090360u); /* 1 */
	FF ( d, a, b, c, in[ 1], S12, 3905402710u); /* 2 */
	FF ( c, d, a, b, in[ 2], S13,  606105819u); /* 3 */
	FF ( b, c, d, a, in[ 3], S14, 3250441966u); /* 4 */
	FF ( a, b, c, d, in[ 4], S11, 4118548399u); /* 5 */
	FF ( d, a, b, c, in[ 5], S12, 1200080426u); /* 6 */
	FF ( c, d, a, b, in[ 6], S13, 2821735955u); /* 7 */
	FF ( b, c, d, a, in[ 7], S14, 4249261313u); /* 8 */
	FF ( a, b, c, d, in[ 8], S11, 1770035416u); /* 9 */
	FF ( d, a, b, c, in[ 9], S12, 2336552879u); /* 10 */
	FF ( c, d, a, b, in[10], S13, 4294925233u); /* 11 */
	FF ( b, c, d, a, in[11], S14, 2304563134u); /* 12 */
	FF ( a, b, c, d, in[12], S11, 1804603682u); /* 13 */
	FF ( d, a, b, c, in[13], S12, 4254626195u); /* 14 */
	FF ( c, d, a, b, in[14], S13, 2792965006u); /* 15 */
	FF ( b, c, d, a, in[15], S14, 1236535329u); /* 16 */

	/* Round 2 */
#define S21 5
#define S22 9
#define S23 14
#define S24 20
	GG ( a, b, c, d, in[ 1], S21, 4129170786u); /* 17 */
	GG ( d, a, b, c, in[ 6], S22, 3225465664u); /* 18 */
	GG ( c, d, a, b, in[11], S23,  643717713u); /* 19 */
	GG ( b, c, d, a, in[ 0], S24, 3921069994u); /* 20 */
	GG ( a, b, c, d, in[ 5], S21, 3593408605u); /* 21 */
	GG ( d, a, b, c, in[10], S22,   38016083u); /* 22 */
	GG ( c, d, a, b, in[15], S23, 3634488961u); /* 23 */
	GG ( b, c, d, a, in[ 4], S24, 3889429448u); /* 24 */
	GG ( a, b, c, d, in[ 9], S21,  568446438u); /* 25 */
	GG ( d, a, b, c, in[14], S22, 3275163606u); /* 26 */
	GG ( c, d, a, b, in[ 3], S23, 4107603335u); /* 27 */
	GG ( b, c, d, a, in[ 8], S24, 1163531501u); /* 28 */
	GG ( a, b, c, d, in[13], S21, 2850285829u); /* 29 */
	GG ( d, a, b, c, in[ 2], S22, 4243563512u); /* 30 */
	GG ( c, d, a, b, in[ 7], S23, 1735328473u); /* 31 */
	GG ( b, c, d, a, in[12], S24, 2368359562u); /* 32 */

	/* Round 3 */
#define S31 4
#define S32 11
#define S33 16
#define S34 23
	HH ( a, b, c, d, in[ 5], S31, 4294588738u); /* 33 */
	HH ( d, a, b, c, in[ 8], S32, 2272392833u); /* 34 */
	HH ( c, d, a, b, in[11], S33, 1839030562u); /* 35 */
	HH ( b, c, d, a, in[14], S34, 4259657740u); /* 36 */
	HH ( a, b, c, d, in[ 1], S31, 2763975236u); /* 37 */
	HH ( d, a, b, c, in[ 4], S32, 1272893353u); /* 38 */
	HH ( c, d, a, b, in[ 7], S33, 4139469664u); /* 39 */
	HH ( b, c, d, a, in[10], S34, 3200236656u); /* 40 */
	HH ( a, b, c, d, in[13], S31,  681279174u); /* 41 */
	HH ( d, a, b, c, in[ 0], S32, 3936430074u); /* 42 */
	HH ( c, d, a, b, in[ 3], S33, 3572445317u); /* 43 */
	HH ( b, c, d, a, in[ 6], S34,   76029189u); /* 44 */
	HH ( a, b, c, d, in[ 9], S31, 3654602809u); /* 45 */
	HH ( d, a, b, c, in[12], S32, 3873151461u); /* 46 */
	HH ( c, d, a, b, in[15], S33,  530742520u); /* 47 */
	HH ( b, c, d, a, in[ 2], S34, 3299628645u); /* 48 */

	/* Round 4 */
#define S41 6
#define S42 10
#define S43 15
#define S44 21
	II ( a, b, c, d, in[ 0], S41, 4096336452u); /* 49 */
	II ( d, a, b, c, in[ 7], S42, 1126891415u); /* 50 */
	II ( c, d, a, b, in[14], S43, 2878612391u); /* 51 */
	II ( b, c, d, a, in[ 5], S44, 4237533241u); /* 52 */
	II ( a, b, c, d, in[12], S41, 1700485571u); /* 53 */
	II ( d, a, b, c, in[ 3], S42, 2399980690u); /* 54 */
	II ( c, d, a, b, in[10], S43, 4293915773u); /* 55 */
	II ( b, c, d, a, in[ 1], S44, 2240044497u); /* 56 */
	II ( a, b, c, d, in[ 8], S41, 1873313359u); /* 57 */
	II ( d, a, b, c, in[15], S42, 4264355552u); /* 58 */
	II ( c, d, a, b, in[ 6], S43, 2734768916u); /* 59 */
	II ( b, c, d, a, in[13], S44, 1309151649u); /* 60 */
	II ( a, b, c, d, in[ 4], S41, 4149444226u); /* 61 */
	II ( d, a, b, c, in[11], S42, 3174756917u); /* 62 */
	II ( c, d, a, b, in[ 2], S43,  718787259u); /* 63 */
	II ( b, c, d, a, in[ 9], S44, 3951481745u); /* 64 */

	buf[0] += a;
	buf[1] += b;
	buf[2] += c;
	buf[3] += d;
}

static const unsigned char ConfigurationDigestSignatureKey [16] = { 0x13, 0xAC, 0x06, 0xA6, 0x2E, 0x47, 0xFD, 0x51, 0xF9, 0x5D, 0x2B, 0xA2, 0x43, 0xCD, 0x03, 0x46 };

void HMAC_MD5_Init (HMAC_MD5_CONTEXT* context)
{
	// perform inner MD5
	// inner padding - key XORd with ipad
	unsigned char k_ipad [65]; 
	memset (k_ipad, 0, sizeof k_ipad);
	memcpy (k_ipad, ConfigurationDigestSignatureKey, sizeof (ConfigurationDigestSignatureKey));
	for (int i = 0; i < 64; i++)
		k_ipad [i] ^= 0x36;

	// init context for 1st pass
	// start with inner pad
	MD5Init (context);					
	MD5Update (context, k_ipad, 64);
}

void HMAC_MD5_Update (HMAC_MD5_CONTEXT* context, const void* text, unsigned int text_len)
{
	MD5Update (context, (const unsigned char*) text, text_len);
}

void HMAC_MD5_End (HMAC_MD5_CONTEXT* context)
{
	// finish up 1st pass
	MD5Final (context, context->digest);

	// perform outer MD5
	unsigned char k_opad[65];
	memset (k_opad, 0, sizeof k_opad);
	memcpy (k_opad, ConfigurationDigestSignatureKey, sizeof (ConfigurationDigestSignatureKey));
	for (int i = 0; i < 64; i++)
		k_opad[i] ^= 0x5c;

	// init context for 2nd pass
	MD5Init (context);
	
	// start with outer pad
	MD5Update (context, k_opad, 64);

	// then results of 1st hash
	MD5Update (context, context->digest, 16);

	// finish up 2nd pass
	MD5Final (context, context->digest);
}

